Refactor notification center to use generics.

core-api/src/main/java/com/optimizely/ab/Optimizely.java

@@ -254,8 +254,12 @@ private void sendImpression(@Nonnull ProjectConfig projectConfig,
                 logger.error("Unexpected exception in event dispatcher", e);
             }
 
-            notificationCenter.sendNotifications(NotificationCenter.NotificationType.Activate, experiment, userId,
-                filteredAttributes, variation, impressionEvent);
+            // Kept For backwards compatibility.
+            // This notification is deprecated and the new DecisionNotifications
+            // are sent via their respective method calls.
+            ActivateNotification activateNotification = new ActivateNotification(
+                experiment, userId, filteredAttributes, variation, impressionEvent);
+            notificationCenter.send(activateNotification);
         } else {
             logger.info("Experiment has \"Launched\" status so not dispatching event during activation.");
         }
@@ -330,8 +334,10 @@ public void track(@Nonnull String eventName,
             logger.error("Unexpected exception in event dispatcher", e);
         }
 
-        notificationCenter.sendNotifications(NotificationCenter.NotificationType.Track, eventName, userId,
+        TrackNotification notification = new TrackNotification(eventName, userId,
             copiedAttributes, eventTags, conversionEvent);
+
+        notificationCenter.send(notification);
     }
 
     //======== FeatureFlag APIs ========//
@@ -419,7 +425,8 @@ public Boolean isFeatureEnabled(@Nonnull String featureKey,
             .withSource(decisionSource)
             .withSourceInfo(sourceInfo)
             .build();
-        notificationCenter.sendNotifications(decisionNotification);
+
+        notificationCenter.send(decisionNotification);
 
         logger.info("Feature \"{}\" is not enabled for user \"{}\".", featureKey, userId);
         return featureEnabled;
@@ -695,7 +702,7 @@ <T extends Object> T getFeatureVariableValueForType(@Nonnull String featureKey,
             .build();
 
 
-        notificationCenter.sendNotifications(decisionNotification);
+        notificationCenter.send(decisionNotification);
 
         return (T) convertedValue;
     }
@@ -790,7 +797,7 @@ public Variation getVariation(@Nonnull Experiment experiment,
             .withType(notificationType)
             .build();
 
-        notificationCenter.sendNotifications(decisionNotification);
+        notificationCenter.send(decisionNotification);
 
         return variation;
     }
@@ -919,6 +926,31 @@ private boolean validateUserId(String userId) {
         return copiedAttributes;
     }
 
+    //======== Notification APIs ========//
+
+    public NotificationCenter getNotificationCenter() {
+        return notificationCenter;
+    }
+
+    /**
+     * Convenience method for adding DecisionNotification Handlers
+     */
+    public int addDecisionNotificationHandler(NotificationHandler<DecisionNotification> handler) {
+        NotificationManager<DecisionNotification> manager = notificationCenter
+            .getNotificationManager(DecisionNotification.class);
+        return manager.addHandler(handler);
+    }
+
+    /**
+     * Convenience method for adding TrackNotification Handlers
+     */
+    public int addTrackNotificationHandler(NotificationHandler<TrackNotification> handler) {
+        NotificationManager<TrackNotification> notificationManager =
+            notificationCenter.getNotificationManager(TrackNotification.class);
+        return notificationManager.addHandler(handler);
+    }
+
+
     //======== Builder ========//
 
     public static Builder builder(@Nonnull String datafile,

core-api/src/main/java/com/optimizely/ab/notification/ActivateNotification.java

@@ -0,0 +1,82 @@
+/**
+ *
+ *    Copyright 2019, Optimizely and contributors
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *        http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+package com.optimizely.ab.notification;
+
+import com.optimizely.ab.annotations.VisibleForTesting;
+import com.optimizely.ab.config.Experiment;
+import com.optimizely.ab.config.Variation;
+import com.optimizely.ab.event.LogEvent;
+
+import java.util.Map;
+
+/**
+ * ActivateNotification supplies notification for AB activatation.
+ *
+ * @deprecated in favor of {@link DecisionNotification} which provides notifications for Experiment, Feature
+ * and Rollout decisions.
+ */
+@Deprecated
+public final class ActivateNotification {
+
+    private final Experiment experiment;
+    private final String userId;
+    private final Map<String, ?> attributes;
+    private final Variation variation;
+    private final LogEvent event;
+
+    @VisibleForTesting
+    ActivateNotification() {
+        this(null, null, null, null, null);
+    }
+
+    /**
+     * @param experiment - The experiment object being activated.
+     * @param userId     - The userId passed into activate.
+     * @param attributes - The filtered attribute list passed into activate
+     * @param variation  - The variation that was returned from activate.
+     * @param event      - The impression event that was triggered.
+     */
+    public ActivateNotification(Experiment experiment, String userId, Map<String, ?> attributes, Variation variation, LogEvent event) {
+        this.experiment = experiment;
+        this.userId = userId;
+        this.attributes = attributes;
+        this.variation = variation;
+        this.event = event;
+    }
+
+    public Experiment getExperiment() {
+        return experiment;
+    }
+
+    public String getUserId() {
+        return userId;
+    }
+
+    public Map<String, ?> getAttributes() {
+        return attributes;
+    }
+
+    public Variation getVariation() {
+        return variation;
+    }
+
+    public LogEvent getEvent() {
+        return event;
+    }
+
+
+}

core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListener.java

@@ -24,15 +24,24 @@
 import javax.annotation.Nonnull;
 import java.util.Map;
 
+/**
+ * ActivateNotificationListener handles the activate event notification.
+ *
+ * @deprecated along with {@link ActivateNotification} and users should implement
+ * NotificationHandler<DecisionNotification> directly.
+ */
 @Deprecated
-public abstract class ActivateNotificationListener implements NotificationListener, ActivateNotificationListenerInterface {
+public abstract class ActivateNotificationListener implements NotificationHandler<ActivateNotification>, NotificationListener, ActivateNotificationListenerInterface {
 
     /**
      * Base notify called with var args.  This method parses the parameters and calls the abstract method.
      *
      * @param args - variable argument list based on the type of notification.
+     *
+     * @deprecated by {@link ActivateNotificationListener#handle(ActivateNotification)}
      */
     @Override
+    @Deprecated
     public final void notify(Object... args) {
         assert (args[0] instanceof Experiment);
         Experiment experiment = (Experiment) args[0];
@@ -51,6 +60,17 @@ public final void notify(Object... args) {
         onActivate(experiment, userId, attributes, variation, logEvent);
     }
 
+    @Override
+    public final void handle(ActivateNotification message) {
+        onActivate(
+            message.getExperiment(),
+            message.getUserId(),
+            message.getAttributes(),
+            message.getVariation(),
+            message.getEvent()
+        );
+    }
+
     /**
      * onActivate called when an activate was triggered
      *

core-api/src/main/java/com/optimizely/ab/notification/ActivateNotificationListenerInterface.java

@@ -23,6 +23,12 @@
 import javax.annotation.Nonnull;
 import java.util.Map;
 
+/**
+ * ActivateNotificationListenerInterface provides and interface for activate event notification.
+ *
+ * @deprecated along with {@link ActivateNotification} and {@link ActivateNotificationListener}
+ * and users should implement NotificationHandler<DecisionNotification> directly.
+ */
 @Deprecated
 public interface ActivateNotificationListenerInterface {
     /**

core-api/src/main/java/com/optimizely/ab/notification/DecisionNotification.java

@@ -29,7 +29,7 @@
 import static com.optimizely.ab.notification.DecisionNotification.ExperimentDecisionNotificationBuilder.EXPERIMENT_KEY;
 import static com.optimizely.ab.notification.DecisionNotification.ExperimentDecisionNotificationBuilder.VARIATION_KEY;
 
-public class DecisionNotification {
+public final class DecisionNotification {
     protected String type;
     protected String userId;
     protected Map<String, ?> attributes;